chemistry 1211
Based on the bond energies for the reaction below, what is the enthalpy of the reaction? H₂ (g) + N₂ (g) + 2 C (g) → 2 HCN (g)
-1223 kJ
What is the bond order of H₂⁺?
0.5
What is the energy of light that must be absorbed by a hydrogen atom to transition an electron from n = 3 to n = 5?
1.55 × 10⁻¹⁹ J
How many electrons can be assigned to orbitals designated by the quantum numbers n = 5, ℓ = 2?
10
Determine the mass, in grams, of 0.820 moles of Pb (1 mol of Pb has a mass of 207.2 g).
169.9 g
How many moles of H₂ are required to produce -5251 kJ of heat in the following reaction? N₂ (g) + 3 H₂ (g) → 2 NH₃ (g) ∆H° = -91.8 kJ/mol
171.6 mol
What is the electron configuration of Co²⁺? A) 1s²2s²2p⁶3s²3p⁶3d⁵ B) 1s²2s²2p⁶3s²3p⁶4s²3d⁵ C) 1s²2s²2p⁶3s²3p⁶4s²3d⁹ D) 1s²2s²2p⁶3s²3p⁶3d⁷ E) 1s²2s²2p⁶3s²3p⁶3d⁹
1s²2s²2p⁶3s²3p⁶3d⁷
How many moles of nitrogen gas would be produced if 8.89 moles of copper(II) oxide were reacted with excess ammonia in the following chemical reaction? 2 NH₃(g) + 3 CuO (s) → 3 Cu(s) + N₂(g) + 3 H₂O(g)
2.96 mol
If 901 J of heat is available, how many grams of iron (specific heat = 0.45 J/g･°C) can be heated from 22.5°C to 120.0°C?
20.5 g
Determine the number of valence electrons in SO₃ and then draw the corresponding Lewis structure (by following the octet rule on all atoms).
24
What is the wavelength of a photon if the energy is 7.59 × 10⁻¹⁹ J? (h = 6.626 × 10⁻³⁴ J • s)
262 nm
Determine the mass in grams of 2.58 × 10²¹ atoms of arsenic. (The mass of one mole of arsenic is 74.92 g.)
3.20 × 10⁻¹ g or 0.321 g ex. look at picture
In the following reaction, how much heat is generated when 4.07 moles of CH₄ are burned? CH₄ (g) + 2 O₂ (g) → CO₂ (g) + 2 H₂O(g) ∆H° = -802 kJ/mol
3264.1 kJ or 3.26 × 10³ kJ
If n = 5, what is the maximum allowed value for ℓ?
4
A 1.2 L weather balloon on the ground has a temperature of 25°C and is at atmospheric pressure (1.0 atm). When it rises to an elevation where the pressure is 0.71 atm, then the new volume is 1.8 L. What is the temperature (in °C) of the air at this elevation?
44 °C
Using the equations 2 C₆H₆ (l) + 15 O₂ (g) → 12 CO₂ (g) + 6 H₂O (g)∆H° = -6271 kJ/mol C (s) + O₂ (g) → CO₂ (g) ∆H° = -393.5 kJ/mol 2 H₂ (g) + O₂ (g) → 2 H₂O (g) ∆H° = -483.6 kJ/mol Determine the enthalpy for the reaction 6 C (s) + 3 H₂ (g) → C₆H₆ (l).
49 kJ/mol
Determine the energy of a photon with a wavelength of 377 nm. (h = 6.626 × 10⁻³⁴ J • s and c = 3.00 × 10⁸ m/s)
5.27 × 10⁻¹⁹ J
A photon has a frequency of 8.49 × 10⁸ Hz. What is the energy of this photon? (h = 6.626 × 10⁻³⁴ J • s)
5.63 × 10⁻²⁵ J
An unknown element X has the following isotopes: ⁵²X (81.50% abundant), ⁴⁹X (8.00% abundant), ⁵⁰X (10.50% abundant). What is the approximate atomic mass of X?
51.6 amu
a popular car has a gas tank that holds a maximum of 14.5 gallons of fuel. What is the size of the tank in liters?
54.9 L
In this reaction: Mg (s) + I₂ (s) → MgI₂ (s) If 2.86 moles of Mg react with 3.56 moles of I₂, and 1.76 moles of MgI₂ form, what is the percent yield?
61.53% ex.picture
How many mL of 0.300 M NaCl solution are required to produce 0.270 moles of NaCl?
900 mL
Which atom in the molecule ClF would have a partial positive charge (δ⁺)?
A) Cl
Classify the following compounds as ionic or covalent: OF₂, CuO, SeO₂.
A) Covalent, ionic, covalent.
Equal amounts of heat are added to equal masses of substances A and B at the same temperature, but substance B gets hotter. What is true of their heat capacities (c)?
A) c(A) > c(B)
An 80.0 g sample of metal, initially at 96.0°C, is placed into 150. g of water initially at 26.0°C in a calorimeter. The final temperature of the water is 28.1°C. What is the identity of the metal? (The specific heat of water is 4.18 J/g･°C.)
Ag
Balance the following chemical reaction: Al₂(SO₄)₃ (aq) + K₃PO₄ (aq) → AlPO₄ (s) + K₂SO₄ (aq)
Al₂(SO₄)₃ (aq) + 2 K₃PO₄ (aq) → 2 AlPO₄ (s) + 3 K₂SO₄ (aq)
In which direction on the periodic table does metallic character increase?
B) Down and to the left.
At the same temperature, which of the following gases will effuse the slowest?
Bromine
Which of the following is an example of an ionic bond?
C) Na - O
Which element has the electron configuration 1s²2s²2p⁶3s²3p⁶4s¹3d⁵?
Cr
Which of the following is true concerning successive ionizations of an atom and its ions?
D) Each successive ionization requires increasing amounts of energy.
The electron configuration of Fe²⁺ is [Ar]3d⁶. Which of the following is true about Fe²⁺? A) Fe²⁺ is diamagnetic. B) Fe²⁺ is paramagnetic with one unpaired electron C) Fe²⁺ is paramagnetic with two unpaired electrons D) Fe²⁺ is paramagnetic with four unpaired electrons. E) Fe²⁺ is paramagnetic with five unpaired electrons.
D) Fe²⁺ is paramagnetic with four unpaired electrons
Draw the Lewis structure of (CHO)OCH₃ and then choose the appropriate set of molecular geometries of the three central atoms. Your answer choice is independent of the orientation of your drawn structure.
D) trigonal planar / bent (109.5º) / tetrahedral
Rank the following atoms in order of decreasing first ionization energies (i.e., highest to lowest): Li, Be, Ba, F.
F > Be > Li > Ba
Rank the following atoms in order of increasing size (i.e., smallest to largest): Li, Al, Be, Ba, O.
O < Be < Li < Al < Ba
What is the correct IUPAC name for Cr₂(SO₄)₃?
chromium(III) sulfate
Write the balanced NET ionic equation for the reaction when BaCl₂ and ZnSO₄ are mixed in aqueous solution. If no reaction occurs, write only NR.
correct answer: Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)
A Lewis structure for sulfate (SO₄²⁻) is shown below, however, its formal charges are not minimized. Starting from this structure, complete the correct structure with minimized formal charges.
picture
A Lewis structure for the nitrate ion (NO₃⁻) is shown on the left below. Draw another equivalent resonance structure of NO₃⁻.
picture
Draw the Lewis structure of acetic acid (CH₃COOH) and then choose the appropriate set hybridization states for the three central atoms. Your answer choice is independent of the orientation of your drawn structure.
sp³ / sp² / sp³
What temperature (in °C) did an ideal gas shift to if it was initially at -21.0 °C at 4.62 atm and 35.0 L and the pressure was changed to 8.71 atm and the volume changed to 15.0 L?
-69.4 °C
The molecular orbital energy diagram for Ne₂ is shown below. Based on this diagram, what is the bond order of Ne₂?
0
A chemist encounters an unknown metal. They drop the metal into a graduated cylinder containing water, and find the volume change is 3.2 mL. If the metal weighs 1.7 g, what is the density of the metal?
0.53 g/mL ex. look at picture
What is the concentration of sodium ions in 0.380 M Na₂CO₃?
0.760 M
How many grams of precipitate will be formed when 20.5 mL of 0.800 M Co(NO₃)₂ reacts with 21.0 mL of 0.800 M NaOH in the following chemical reaction? Co(NO₃)₂ (aq) + 2 NaOH (aq) → Co(OH)₂ (s) + 2 NaNO₃ (aq)
0.781 g ex. look at picture
how many moles of NH3 form when 32.4 L of H2 gas completely react at STP according to the following reaction? Remember 1 mol of an ideal gas has a volume of 22.4 L at STP
0.964 mole NH3
The skeletal structure of a complex organic molecule is shown below. Determine the number of sigma (σ) and pi (π) bonds in the molecule.
34σ and 6π
A barrel of crude oil has a volume of 42 gallons, only approximately 45% of which is processed into gasoline. If your car achieves 28 mi/gal, and you drive 36,000 miles in one year, how many barrels of crude oil are required to run your car for a year?
68 barrels ex.picture
The answer to the calculation below with the correct number of significant figures is
C) 220
Based on their positions in the periodic table, which of the following bonds is the most polar?
C) B - F
Consider the following reaction: Mg²⁺(aq) + Cu(s) → Cu²⁺(aq) + Mg(s). In this reaction, Mg²⁺(aq) is: A) Oxidized B) Reduced C) A reducing agent D) An oxidizing agent E) Both (B) and (D)
E) Both (B) and (D
A student draws the orbital diagram below for the 3d electrons in a V atom. What, if anything, is incorrect about the drawing?
It violates Hund's rule.
Write the chemical formula for phosphorus trihydride
PH₃
Draw the Lewis structure of urea ((NH₂)₂CO) and then determine if the molecule is polar or nonpolar.
Polar
Balance the following chemical equation (if necessary): ~ look at image ~
answer: 2(NH₄)₃PO₄(aq) + 3MgCl₂(aq) → Mg₃(PO₄)₂(s) + 6NH₄Cl(aq)
Write a balanced chemical equation based on the following description: aqueous potassium phosphate reacts with aqueous nickel(II) bromide to produce solid nickel(II) phosphate and aqueous potassium bromide. ~ look at image~
answer:2 K₃PO₄(aq) + 3 NiBr₂(aq) → Ni₃(PO₄)₂(s) + 6 KBr(aq)
Consider the balanced chemical reaction below. How many grams of CaSO₄ can be produced from 1.00 kg of Ca₃(PO₄)₂ and 1.00 kg of H₂SO₄? Ca₃(PO₄)₂(s) + 3 H₂SO₄(aq) → 3 CaSO₄(s) + 2 H₃PO₄(aq)
picture
What type of reaction is represented by the following equation: C₄H₈(g) + 6O₂(g) → 4CO₂(g) + 4H₂O(g)
redox (oxidation-reduction)
All of the following pairs of ions are isoelectronic except which one?
C) Fe²⁺ and Mn³⁺
What is the empirical formula of a compound that contains only iron and oxygen and is 22.27% oxygen? A) FeO B) FeO₂ C) Fe₂O D) Fe₇O₂
A) FeO